Approach controlled railway track circuit system



J n 2 1951 J. R. HENDERSON APPROACH CONTROLLED RAILWAY TRACK CIRCUIT SYSTEM Filed Oct. 23, 1946 m U 2 am a m b r T E 7. m r T A 6 l ENTOR f0/212 614a Q'QPSOIZ.

Ally ATTORNEY Patented June 26, 1951 UNITED STATES PATENT OFFICE APPROACH CONTROLLED RAILWAY TRACK CIRCUIT SYSTEM John Reed Henderson, Wilkinsburg, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application October 23, 1946, Serial No. 705,101

7 Claims.

My invention relates to approach .controlled railway track circuit systems, and particularly to tems it is often desirable to provide means wherewith traffic in a stretch is enabled to control traffic governing devices in advance of the traffic. For example, it may be desirable to have the approach of a traincause the lighting of normally deenergized signals, or control a normally inactive signal to its proper aspect, or look a track switch :against operation. In establishing such control of trafiic governing devices it is customary to use track circuits in which the track rails form the conductors for electric current used to establish the desired control, and it is essential that such track circuit elements be arranged in such manner as to protect against the presence of foreign currentin the track rails.

It is an object of my invention to provide novel and improved'means whereby the approach of a train is utilized to establish control of traific governing devices in advance of a train.

' Another object of my invention is to provide track circuit means for approach controlling circuit current and requiring a minimum of apparatus to obtain protection against foreign current, overlapping coding contacts, and inductive discharge. from the track rails.

Another object of my invention is to provide novel and improved approach controlled means arranged to control traffic governing signals at the opposite ends of a section in response to the approach of a train to that section.

The above-mentioned and other important objects and characteristic features of my invention are obtained by providing a section of track with two track circuits, one comprising a non-coded track circuit in which energy supplied at the entrance end of the section is received at the exit end by "a track relay which is effective when released to cause the application of coded track circuit energy to the second track circuit at the exit end of the section for transmission to the entrance end where it operates dccodingapparasection so as to establish the coded track circuit under such conditions. The coded track circuit is governed by conditions in advance of the section and the two track circuits are utilized in the control of traffic governing devices at the tWo ends of the section respectively.

I shall describe one form of apparatus embodying my invention and shall then point out the novel features thereof in claims.

The accompanying drawing is a diagrammatic view of a preferred form of apparatus embodying my invention.

Referring to the drawing, the reference characters l and to designate the track rails of a stretch of railway track in which trafiic normally operates in the direction indicated by the arrow, or from left to right as viewed in the drawing. The rails I and la are divided by means of insulated joints 2 into a plurality of successive adjoining track sections of which two sections AT and T are represented complete in the drawing. The stretch also includes a track switch W positioned in advanceoi section '1 with its points facing toward trai'fic approaching in the normal direction in the stretch. Switch W is provided with the usual circuit controller including a movable contact member 4 controlled by the position of the switch to close a contact 4-5 when and only when the switch is set inits normal position for trafiic on the stretch. Contact 4 is operated out of engagement with contact member 5 by switch W when the switch is reversed to permit movement of trailic into a passing track P or whenever the points of the switch are not in alignment for main line traffic movements in the stretch. The reference character NWP designates a switch repeater relay energized whenever switch W is normal, over a circuit extending from one terminal B of a suitable source of current such as a battery not shown, through contact 45 operated by switch W, and the winding of relay NWP to the other terminal C of the source of current. The relay NWP therefore constitutes a means controlled by conditions afiecting the movement of traffic in the stretch in advance of section T.

The reference characters with suitably distinguishing prefixes designate signals for controlling the movement of traffic in the stretch. Signal 28 is located at the exit end of section T for governing the movement of traffic over switch W and as shown may comprise a color light signal having two lamps for displaying a green or .red aspect, repectively. Signal 28 is controlled by switch W in a manner to be explained hereinafter so as to function as a switch protection signal. The other signal IS is located at the entrance end of section T, that is at the junction of sections AT and T, and as shown may also comprisea color light signal having two lamps capable of displaying a green or a yellow aspect, respectively. Signal IS is also controlled by the position of switch W in a manner which will be explained hereinafter and therefore may be considered a distant signal for signal 2S.

The section AT is provided in the usual manner with a normally energized direct current track circuit comprising a battery 6 connected across the rails of the section at its entrance end, and a track relay ATR connected across the rails at its exit end. Section T also is provided with track circuit apparatus comprising a track ba tery 1 and a track relay TR at the entrance end of the section; and another track battery 9 and track relay AR at the exit end of the section Either battery 1 or relay TR is connected across the rails at the entrance end of section T according as relay ATR. of the section in the rear is picked up to close its front contact 8 or is released to close contact 8 in its back position. The relay TR has associated therewith decoding means comprising two relays FSA and BSA which operate in a manner that will be pointed out hereinafter. Relays ATR and BSA cooperate in the control of signal IS in such a manner that one lamp or the other of the signal is lighted whenever relay ATR is released to close its back contact ILwith the selection between lamps Y and G of signal IS being established by relay BSA according as that relay is released to close its contact I8 in its back position or is picked up to close contact l8 in its front position, respectively. Both lamps of signal IS are deenergized when relay ATR is picked up and in such a condition the signal is dark.

The relay AR normally is connected across the track rails of section T at its exit end over a stick circuit extending from rail I through the winding -of relay AR and front contact ID. of that relay to the other rail la. Relay. AR controls a repeater relay AP over an obvious circuit including front contact ll of relay AR. Relay AP in mitter CT to terminal C. The transmitter CT has a contact l4 which assumes an intermediate position when the coder is deenergized and which is operable between a first and a second position at a predetermined code rate of, for example, 75

cycles per minute when the coder is energized.

- When contact M of coder CT is in its first position battery 9 is connected across the rails of 3 section T at its exit end, and in the second position of contact [4 the winding of relay AR is connected across the track rails of section T at its exit end in a pick-up circuit. The repeater relay AP and switch repeater relay NWP control signal 2S in such a manner that when both relays are released, lamp'R of signal 2S is energized over an obvious circuit including back contacts l5 and i6 of relays AP and NWP respectively; when relay AP is released and relay NWP is picked up lamp G of signal 2S is energized over a circuit including back contact [5 of relay AP and front contact N5 of relay NWP; and whenever relay AP is picked up the circuits for both lamps G and R of signal 2S are interrupted so that this signal is dark. 7

The apparatus embodying my invention is in its normal condition as represented in the draw ing when both sections AT and T are vacant switch W is in its normal position so that switch repeater relay NWP is energized. In this condition of the apparatus, relay ATR closes its front contact 8 to connect battery 1 across the rails of section T at its entrance end and the rails transmit current from battery 1 to the exit end to energize relay AR over its previously traced stick circuit including its own front contact it. Relay AP also is energized over front contact ll of relay AR and as a result coder CT is deenergized so that its contact [4 occupies its intermediate position. All other apparatus of my invention is deenergized so that both signals IS and 28 are dark.

When a train operating in the normal direction of traific in the stretch enters section AT, relay ATR is shunted and releases to close its back contact l! to energize lamp Y of signal ts over its circuit including back contacts I! and l8 of relays A'I'R and BSA respectively. Contact 8 of relay ATR also operates from its front position to disconnect battery 1 from the rails of section T at its entrance end, to, its back position where relay TR is connected across the track rails of section T. The disconnection of battery I from the rails of section T results in the deenergization of relay AR atthe opposite end of the section, so'

that repeater relay AP releases to close its back contact I5 and energize lamp G of signal 2S. Back contact [2 of relay AP also closes to energize coder CT and set contact l4 into operation. The contact I4 is alternately operated between its first position, in which battery 9 is connected to the track rails of section T at its exit end, and its second position in which the winding of relay AR is connected across the track rails. The periodic connection of battery 9 to the rails of section T results in the supply to the track rails of periodically interrupted or coded current which is transmittedto the entrance end where it intermittently energizes relay TR, but the intermittent connection of relay AR to the track rails over contact [4 of coder CT in its second position has no useful function at this time. The energization of relay TR each time that battery 9 is connected to the track rails, causes relay TR to pick up and close its front contact 20 to energize relay FSA, and the deenergization of relay TR each time battery 9 is disconnected from the track rails by able means, such as a rectifier 22 connected across its terminals, and when relay TR alternately picks up and releases at the predetermined code rate generated by coder CT, theslow release feature of relay FSA maintains its armature picked up during the intervals between code pulses that relay TR is released, so that during these intervals the circuit for relay BSA is completed. Relay BSA also is made slow to release and bridges the intervals that relay TR is picked up. It follows that during operation of relay TR by coded energy applied through contact I4 of coder CT at the exit end of the section, relays FSA and BSA are alternately energized during the energized and deenergized conditions of relay TR respectively, and that when relay BSA picks up under these'con- 5 ditions an indication is provided that relay TR is following code. With relay BSA energized, contact I8 is operated to its front position so that lamp G of signal IS is energized over its obvious circuit.

It follows from the foregoing that when a train enters section AT, the normally established track circuit for section T that includes battery 1 and relay AR is interrupted so that relay AR releases to cause the signal at the exit end of the section to become lighted;- and also to cause coded energy to be supplied at the exit end for operating relay TR at the entrance end. The code operation of relay TR is detected by relay BSA which functions to control signal IS to its clear indication.

When the train enters section T the coded track circuit energy applied to the section rails through contact M of coder CT is shunted away from relay TR and as a result that relay remains in its released position so that both relays FSA and BSA release. This causes lamp Y of signal I IS to be energized over back contact [8 of relay BSA. When the train vacates section AT relay ATR picks up to open its back contact I! and deenergize signal IS, while contact 8 of relay ATR operates from its back position to its front position to disconnect relay TR from the rails of section T and to connect battery 1 to the rails, but as long as the train is in the section it shunts energy from battery i away from the opposite end of the section.

When the train vacates section T, relay AR is supplied with energy from battery 1 over the previously traced pick-up circuit of the relay, which circuit is established each time contact M of coder CT is operated to its second position. Relay AR accordingly picks up over this circuit and closes its front contact l0 to complete its stick circuit which is effective to hold that relay 1 energized during the intervals that contact Id of coder CT is in its front position to connect battery 9 to the rails and disconnect relay AR from its pick-up circuit. The alternate connection of battery 9 to the rails of the section over contact M in its first position, is of no practical effect at this time because relay TR at the entrance end is disconnected from the track rails so that the coded track circuit cannot be established. It is to be noted, however, that when contact I4 is in its first position, a circuit for relay AR is established extending from one terminal of battery 9 through contact l4 of coder CT closed in its first position, front contact ll] of relay AR and the winding of relay AR to the other terminal of battery 9, and that current flows from battery 9 through the relay in the same direction as the direction of current flow in the relay due to battery 1, so that in the first position of contact 14 the relay AR is held up by current from both batteries 1 and 9. The enrgization of relay AR causes relay AP to pick up and deenergize signal 28 at back contact I 5, and coder CT at back contact l2. Coder CT accordingly ceases to operate and positions its contact M in its intermediate position and as a result the apparatus is restored to its normal position as represented in the drawing.

In the event that the switch W is not in its normal position, that is, the switch is reversed or the points are out of adjustment, then contact 45 operated by the switch will be open with the result that relay NWP is released. If a train should enter section AT under these conditions,

"relay at; Will be released when battery 1 is disconnected from the rails of section T by the opening of front contact 8 of relay ATR, and back contact [2 of repeater relay AP will close but since front contact l3 of relay NWP is now open coder CT will not become energized and as a result no coded energy will be applied to the rails of 'section T. Although relay TR is now connected to the rails at the entrance end of sectionT, itdoes not respond to code under the conditions assumed and relay BSA remains released so that lamp Y of signal IS is lighted over its obvious circuit. Also with relay NWP released, lamp R of signal '23 is caused to become lighted over its circuit including back contact l6 of relay NWP. Under these conditions the fact that switch W is not in its normal position is indicated by the lighted red aspect of signal 26 and the lighted yellow aspect of signal [S which functions as a distant signal for signal 28.

For a movement into the passing siding P, no chan e in the apparatus will be effected when th train enters section T but when the train clears section AT relay ATR picks up to open its back contact I! and deenergize signal IS, and also to disconnect relay TR from the track rails and connect battery I to the rails of section '1 over front contact 8. When the train vacates section T the apparatus remains in its last established condition with relay AR released and lamp R of signal 28 lighted because under the conditions assumed the apparatus is not self-restoring. That is, when section T becomes vacated energy from battery 1 is no longer shunted away from the exit end of the section but with coder CT deenergized so that its contact I4 is in from battery 1 cannot reach. relay AR and as a result relay AR remains released. Lamp R of signal 2S accordingly remains lighted to indicate that switch W is not in a position for main line movement, and will remain lighted to indicate this fact until such time as the switch is restored to its normal position. When this happens contact 4--5 operated by the switch closes so that switch repeater relay NWP picks up to close its front contact i3 and. complete the energizing cirmill; for coder CT. Contact M of coder CT thereupon is set into operation and when operated to its second position establishes the previously mentioned pickup circuit for relay AR over which energy from the battery 1 is supplied to that relay. Relay AR accordingly picks up over this intermittently established pick-up circuit and closes its front contact ii to complete its normal stick circuit. Repeater relay AP is energized over front contact ll of relay AR and picks up to open its back contact [5 to deenergize signal 23, and back contact l2 to deenergize coder CT. The operation of coder CT is terminated and contact I4 is positioned in its intermediate position to restore the apparatus to its normal condition as illustrated in the drawing.

From the foregoing description it is readily apparent that the apparatus embodying my invention is arranged so that a train approaching sec tion T interrupts the normally established track circuit for that section and causes signal 28 at the exit end of that section to display a lighted aspect determined by conditions in advance of that signal, and if conditions are proper establishes another track circuit for the section which causes the aspect displayed by signal IS to refleet conditions in advance of the section. Signal most restrictive (Y) aspect.

IS is lighted by the train in section AT but the control of the aspect of the signal is established by means of a track circuit which is completed only if conditions in advance of section T are favorable for main line movements so that signal IS constitutes an approach signal for the other signal 28 at the exit end of the section. It is to be seen therefore that the track circuit for section T' comprising battery I and relay AR is controlled by traffic conditions in the rear of section T, while the coded track circuit for section T comprising battery 9 and relay TR. is controlled by conditions in advance of section T.

The apparatus embodying my invention is arranged to provide protection against foreign currents in section T. That is, if current from a foreign source is present in the track rails of a nature such as to energize relay AR, the fact that relay AR might be held up by this current even though battery I is disconnected from the track rails by the release of relay ATR results in holding repeater relay AP picked up so that both signalZS and coder CT remain deenergized. Under this condition signal 2S remains dark while signal IS displays its lighted yellow aspect to provide an indication that the train should be prepared to stop at the next, signal. Any failure of the apparatus due to foreign current in the track rails of section T therefore provides a safe failure in that signal 28 will be held dark while signal IS will be controlled to its most restrictive aspect.

similarly apparatu embodying my invention provides protection against both overlapping coding contacts and inductive discharge from the track rails. If contact I4 of coder CT should become deranged so that the contact completes both its front and back points simultaneously instead of alternatively, energy from 7 battery 9 will be provided with a circuit through contact l4 and the winding of relay AR, and as a result relay AR will tend to pick up and energize relay AP so as to deenergize coder CT. Similarly, if conditions in section T are such as to cause energy in the rails to discharge inductively during the period when relay AR is 7 protection against unsafe failures of the apparatus because energization of relay AR will result in energization of relay AP, thereby controlling signal 25 to a restrictive (dark) aspect, and in the denergization of coder CT which results in limiting control of signal is to its The arrangement of the apparatus is thus such that possibility of abnormal operating conditions cannot cause the signals to display aspects less restrictive than warranted under the conditions.

Although I have herein shown and described only one form of approach controlled railway track circuit system embodying my invention, it is to be understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of myinvention Having thus described my invention, what I claim is:

1. In combination with a stretch of railroad track divided by insulated joints into two successive adjoining, track sections, a first normally deenergized signal at the junction of said two sections for governing traffic in a given direction in one of said sections, a second normally deenergized signal at the opposite end of said one section for governing traffiic in said given direction beyond the opposite end of said one section, a first source of current and a first track relay at said opposite end of said one section, a coding device having a contact operable between a first and a second position and biased to a position intermediate said first and second positions, means governed by conditions affecting the movement of traific in said stretch beyond the opposite end of said one section, means controlled by said first track relay and by said condition governed means for operating said coding device, means controlled by said contact of said coding device for connecting either said first source or said first track relay inscircuit with the rails of said one section at said opposite end according as said contact is in its said first or second position respectively, a stick circuit including a front contact of said first track relay for connecting said first track relay in circuit with the rails of said one section at said opposite section end, means controlled by said first track relay when released for causing said second signal to display a lighted aspect governed by said condition governed means, a second source of current and a second track relay at the junction end of said one section, means controlled by tramc in the other of said sections for connecting either said second source or said second track relay in circuit with the rails of said one section at said junction end according as said other section is vacant or occupied respectively, decoding means for detecting code operation of. said second track relay, and means governed by said traflic controlled means for causing said first signal to display a lighted aspect governed by said decoding means.

2. In combination with a stretch ofrailroad track including a track switch and two adjoining track sections, said track sections being located in approach to the points of said track switch, a firstsignal at the junction of said two sections for governing traffic in one of said sections approaching said switch, a second signal 'at'the opposite end of said one section for governing traiiic in said one direction over said switch, a first source of current and a first relay at said opposite end of saidbne section, a coding device having a contact operable between a first and a second position and biased to a position intermediate said first and second positions, means controlled by said first relay and by said track switch for operating said coding device, means controlled by said contact of said codin device for connecting either said first source or said first relay in circuit with the rails of said one section at said opposite end according as said contact is in its said first or second position respectively, a stick circuit including a front contact of said first relay for connecting said first relay in circuit with the rails of said one section at said opposite section end, means governed by said'track switch for controlling said second signal, a second source of current and a second'relay at the junction end of said one section, means controlled'by trafiic in the other of said sections'for connecting either said second source or said second relay in circuit with the rails of said one section at said junction end according as said other section is vacant or occupied respectively, decoding means for de- 9 tecting code operation of said second track relay, and means controlled by said decoding means for controlling said first signal.

3.. In combination with a stretch of railroad track including an insulated track section, a traffic controlling device at one end of said section, a first source of current and a first relay at the opposite end of said section, a coding device having a contact operable between a first and a second position and biased to a position intermediate said first and second positions, means controlled by conditions affecting the movement of trafiic in said stretch beyond said opposite end of said section, means controlled by said first relay and by said condition controlled means for operating said coding device, means controlled by said contact of said coding device for connecting either said first source or said first relay in circuit with the rails of said section at said opposite end according as said contact is in its said first or second position respectively, a stick circuit including a front contact of said first relay for connecting said first relay in circuit with the rails of said section at said opposite section end, a second source of current and a second relay at the one end of said section, means controlled by trafiic conditions in said stretch beyond the one end of said section for connecting either said second source or said second relay in circuit with the rails of said one section, decoding means for detecting code operation of said second relay, and means governed by said decoding means for controlling said trafiic controlling device.

4. In combination with a stretch of railroad track including an insulated track section, a first trafiic controlling device at one end of said section, a second traffic controlling device at the opposite end of said section, a first source of current and a first relay at said opposite end of said section, a coding device having a contact operable between'a first and a second position and biased to a position intermediate said first and second positions, means controlled by conditions affecting the movement of trafiic in said stretch beyond said opposite end of said section, means controlled by said first relay and by said condition controlled means for operating said coding device, means controlled by said contact of said coding device for connecting either said first source or said first relay in cir cuit with the rails of said section. at said opposite end according as said contact is in its said first or second position respectively, a stick circuit including a front contact of said first relay for connecting said first relay in circuit with the rails of said section at said opposite section end, means governed by said first relay for controlling said second traffic controlling device, a second source of current and a second relay at the one end of said section, means controlled by traffic conditions in said stretch beyond the one end of said section for connecting either said second source or said second relay in circuit with the rails of said one section, decoding means for detecting code operation of said second track relay, and means governed by said decoding means for controlling said first traffic controlling device.

5. In combination with a stretch of railroad track including an insulated track section, a first signal at one end of said section. for governing traific in a given direction in said section, a second signal at the opposite end of said section for governing traflic in said given direction beyond the opposite end of said section, a first source of current and a first track relay at said opposite end of said section, a coding device having a contact operable between a first and a second position and biased to a position intermediate said first and second positions, means governed by track conditions in said stretch beyond the opposite end of said section, means controlled by said first track relay and by said condition governed means for operating said coding device, means controlled by said contact of said coding device for connecting either said first source or said first relay in circuit with the rails of said section at said opposite end according as said contact is in its said first or second position respectively, a stick circuit including a front contact of said first relay for connecting said, first relay in circuit with the rails of said section at said opposite section end, means governed by said first track relay and by said condition governed means for controlling said second signal, a second source of current and a second track relay at the one end of said section, means controlled by trafiic conditions in said stretch beyond the one end of said section for connecting either said second source or said second track relay in circuit with the rails of said section at said one end according as trafiic is not or is approaching said section respectively, decoding means for detecting code operation of said second track relay, and means controlled by said decoding means for controlling said first signal.

6. In combination with a stretch of railroad track including a track switch and an insulated track section, said track section being located in approach to the points of said track switch, a first signal at one end of said section for governing trafiic in said section approaching said switch, a second signal at the opposite end of said section for governing traffic in said one direction over said switch, a first source of current and a first track relay at said opposite end of said section, a coding device having a contact operable between a first and a second position and biased to a position intermediate said first and second positions, means governed by the position of said track switch, means controlled by said first track relay and by said switch controlled means for operating said coding device, means controlled by said contact of said coding device for connecting either said first source or said first relay in circuit with the rails of said section at said opposite end according as said contact is in its said first or second position respectively, a stick circuit including a front contact of said first relay for connecting said first relay in circuit with the rails of said section at said opposite section end, means controlled by said first track relay and by said switch controlled means for governing said second signal, a second source of current and a second track relay at the: one end of said section, means controlled by traffic beyond the one end of said section, means controlled by said trafiic controlled means for conll track section, said track section being located in approach to the points of said track switch, a home signal at the one end of said section for governing trafiic over said switch, a distant signal at the opposite end of said section for said home signal, a first source of current and a first track relay at said one end of said section, a coding device having a contact operable between a first and a second position and biased to a position intermediate said first and second positions, means controlled by the position of said switch, means controlled by said first track relay and by said switch controlled means for operating said coding device provided said first track relay is released and said switch is positioned for main line movements in said stretch, means controlled by said contact of said coding device for connecting either said first source or said first relay in circuit with the rails of said section at said one end according as said contact is in its said first'2o or second position respectively, a stick circuit including a front contact of said first relay for connecting said first relay in circuit with the rails of said section at said one section end,

12 means controlled by said first track relay when released for causing said home signal to display a lighted aspect indicating clear or danger according as said switch is or is not positioned for main line movements respectively, a second source of current and a second track relay at said opposite end of said section, means controlled by traffic beyond said opposite end of said section, means governed by said traffic controlled means for connecting either said second source or said second track relay in circuit with the rails of said section at said opposite endaccording'as traffic is not or is approaching said section respectively, decoding means for detecting code operation of said second track relay, and means controlled by said traific controlled means for causing said distant signal to display a lighted aspect indicating clear or caution according as code operation of said second track relay is or is not' detected by said decoding means.

JOHN REED HENDERSON.

No references cited. 

